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Questions and Answers
Sensory stimuli enter the spinal cord via?
Sensory stimuli enter the spinal cord via?
- Afferent axons (correct)
- Efferent axons
- Interneurons
- Sensory receptors
How many neurons typically involve a simple spinal reflex?
How many neurons typically involve a simple spinal reflex?
3
Interneurons are located in the?
Interneurons are located in the?
- Sensory receptors
- Skin
- Spinal cord (correct)
- Effector organ
Where are sensory receptors found?
Where are sensory receptors found?
Simple spinal reflexes occur independent of the brain.
Simple spinal reflexes occur independent of the brain.
Damage to the ventral root of a spinal nerve would mean that the sensory input of the reflex arc would be interrupted.
Damage to the ventral root of a spinal nerve would mean that the sensory input of the reflex arc would be interrupted.
A reflex arc must involve interneurons for processing in the spinal cord.
A reflex arc must involve interneurons for processing in the spinal cord.
What is the simplest reflex that causes muscles to contract in response to a stretch?
What is the simplest reflex that causes muscles to contract in response to a stretch?
What prevents contracting muscles from applying tension to tendons?
What prevents contracting muscles from applying tension to tendons?
What reflex removes a body part from a painful stimulus?
What reflex removes a body part from a painful stimulus?
What response to a withdrawal reflex causes extension of the opposite limb?
What response to a withdrawal reflex causes extension of the opposite limb?
What type of reflex involves excitation of agonists and inhibition of antagonists?
What type of reflex involves excitation of agonists and inhibition of antagonists?
What reflex involves excitation of flexors and inhibition of extensors?
What reflex involves excitation of flexors and inhibition of extensors?
What reflex is marked by actions to stabilize the limb opposite of injurious agents?
What reflex is marked by actions to stabilize the limb opposite of injurious agents?
What receptors are the tendon organs?
What receptors are the tendon organs?
What sensory receptors monitor changes in muscle tension?
What sensory receptors monitor changes in muscle tension?
What results in maintained stretch of the central region of the intrafusal fibers?
What results in maintained stretch of the central region of the intrafusal fibers?
What sensory receptors monitor muscle length and the rate of change in muscle length?
What sensory receptors monitor muscle length and the rate of change in muscle length?
What removes tension on the stretch receptors and lowers the rate of action potential firing?
What removes tension on the stretch receptors and lowers the rate of action potential firing?
What connective tissue capsule contains intrafusal muscle fibers?
What connective tissue capsule contains intrafusal muscle fibers?
What activates spindle stretch receptors and causes an increased rate of action potential in the afferent neuron?
What activates spindle stretch receptors and causes an increased rate of action potential in the afferent neuron?
What are modified skeletal muscle fibers within a muscle spindle called?
What are modified skeletal muscle fibers within a muscle spindle called?
What small motor neuron controls the intrafusal muscle fibers?
What small motor neuron controls the intrafusal muscle fibers?
What skeletal muscle fibers generate force and movement?
What skeletal muscle fibers generate force and movement?
What large motor neurons control the extrafusal muscle fibers?
What large motor neurons control the extrafusal muscle fibers?
What reflex test is associated with the knee?
What reflex test is associated with the knee?
What reflex is tested by hitting the inside of the elbow?
What reflex is tested by hitting the inside of the elbow?
What is the normal response to striking the foot?
What is the normal response to striking the foot?
What term describes a diminished or absent reflex that may suggest muscle disease?
What term describes a diminished or absent reflex that may suggest muscle disease?
What term describes an abnormally strong reflex that may indicate damage in the brain?
What term describes an abnormally strong reflex that may indicate damage in the brain?
Rhythmic oscillations between flexion and extension when the muscle reflex is tested are called ____________.
Rhythmic oscillations between flexion and extension when the muscle reflex is tested are called ____________.
What tracts from the spinal cord to thalamus are located in the pons?
What tracts from the spinal cord to thalamus are located in the pons?
What laterally pathway carries somatic sensory information in the medulla oblongata?
What laterally pathway carries somatic sensory information in the medulla oblongata?
The _____________ tract relays proprioceptive information to the cerebellum for processing.
The _____________ tract relays proprioceptive information to the cerebellum for processing.
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Study Notes
Nervous System Basics
- Sensory stimuli are transmitted to the spinal cord through afferent axons.
- A simple spinal reflex typically involves three neurons: a sensory neuron, an interneuron, and a motor neuron.
- Interneurons are primarily found in the spinal cord, facilitating communication between sensory and motor pathways.
- Sensory receptors are distributed throughout the body, not limited to specific areas like the brain or spinal cord.
Reflexes and Reflex Arcs
- Simple spinal reflexes can occur independently of the brain, confirming the body's ability to process reflexes locally.
- Reflex arc sequence:
- Sensory receptor detects stimulus.
- Sensory neuron sends action potentials to the spinal cord.
- Interneuron may synapse with a motor neuron.
- Motor neuron carries signals to the effector organ (muscle or gland).
- Damage to the ventral root of a spinal nerve affects motor output, not sensory input.
Types of Reflexes
- The stretch reflex causes muscle contraction in response to a stretch.
- The Golgi tendon reflex prevents excessive tension in muscles.
- Withdrawal reflex removes the body part from painful stimuli.
- Crossed extensor reflex stabilizes the opposite limb during injury.
Muscle Spindles and Tension Regulation
- Muscle spindle receptors monitor muscle length and its change rate.
- Golgi tendon organs monitor muscle tension.
- Alpha-gamma coactivation maintains stretch in intrafusal fibers, regulating action potential firing.
- Extrafusal fiber contraction reduces tension on stretch receptors.
Muscle Reflexes
- Passive muscle stretch activates spindle stretch receptors, increasing action potential rates in afferent neurons.
- Intrafusal fibers are modified skeletal muscle fibers within the muscle spindle.
- Gamma motor neurons control intrafusal muscle fibers, while alpha motor neurons control extrafusal muscle fibers.
Assessing Reflex Responses
- Myotatic reflex tested by tapping the knee results in a quick contraction.
- Biceps reflex assessed by hitting the inside of the elbow evaluates upper limb responses.
- Normal response to foot stimulation is toe flexion.
- Hypoactive reflex indicates potential muscle disease or neuromuscular junction damage.
- Hyperactive reflex signals possible brain damage and may present with clonus, characterized by rhythmic oscillations of muscle contraction.
Pathways for Sensory Information
- Spinothalamic tracts relay sensory information from the spinal cord to the thalamus.
- Dorsal column-medial lemniscus pathway carries somatic sensory information through the medulla oblongata.
- Spinocerebellar tracts relay proprioceptive information to the cerebellum for processing.
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